Sugar being blamed for a child’s hyperactivity is a myth. Aaron Carroll over at The Incidental Economist explains:
In my favorite of these studies, children were divided into two groups. All of them were given a sugar-free beverage to drink. But half the parents were told that their child had just had a drink with sugar. Then, all of the parents were told to grade their children’s behavior. Not surprisingly, the parents of children who thought their children had drunk a ton of sugar rated their children as significantly more hyperactive. This myth is entirely in parents’ heads. We see it because we believe it.
So if your kids acted up over Halloween, it’s not due to the candy.